We propose to utilize the outcomes of concerted post hoc (ex-post) efforts to compare existing data on subjective well-being (SWB) collected in the contexts of the Health and Retirement Study (HRS) and English Longitudinal Study of Aging (ELSA) to develop a priori (ex-ante) harmonization strategies to facilitate future innovative comparative research on this topic. Our overall aim is to compare cross-national trends and correlates of SWB in populations aged 50- and-older using the extensive data available from these studies. Previous efforts at ex-post HRS-ELSA comparisons have focused on the role of socioeconomic factors in health (Banks, Marmot, Oldfield, &Smith, 2006). This important pioneering research pointed to the scientific and policy value of exploring trends in health status observed in nationally representative surveys the US and England because of the different demographic structures and social contexts of the aged populations in each country. Cross-national comparisons of well-being would complement and extend this initial work. Like physical health, measures of SWB (e.g. life satisfaction, positive and negative affect) are important components of life quality and successful aging. However, before such HRS-ELSA analyses on SWB can be undertaken, a platform is needed to facilitate the exchange of data and information between researchers from each project. Preliminary analyses of well-being indicators suggest that, although the potential to conduct cross-national comparisons exists, several methodological issues need to be addressed. These include the possible confounding effects of measurement differences and the impact of sample composition and attrition. Ideally harmonization of measurement should occur prior to data collection if cross-national comparison is intended. To this end, we plan to use the opportunity provided by the HRS-ELSA exchanges and secondary analyses to develop new ways to assess SWB (e.g., by combining time-use and evaluative self-report data on activities). This will serve to optimize future cross-national comparisons not only between HRS and ELSA but also with countries in the SHARE network. PUBLIC HEALTH RELEVANCE: Project Narrative This project will establish a platform to consolidate and compare information about the level and correlates of subjective well-being in the over-50 population in the USA, UK and mainland Europe. Comparisons of well-being in countries with different demographic structures and rates of aging, provide important information about the differential efficacy of national health, financial, and social policies to ensure the life quality of their older citizens and minimize disparities within and between generations.